The advantage of TV is reach. You collect a lot of money, give it to the television industry and many people are 'able' to see your campaign appeal. If it is a congressional district the reach is in the tens or hundreds of thousands. For senate races the required reach usually will be millions.

Campaign ads are old media. The first presidential campaign ads were in 1952. Campaign ads for congressional candidates had to wait for cable TV. Email, which is now being used so enthusiastically to importune us to send money, started in the 1960s. The software that makes it easy to do the mass mailing is more recent, but this is still old technology.

There is new media technology. Does any of it offer comparable reach? Microblogging, usually with Twitter, does if you understand the Twitter two-step. With Twitter people may sign up to follow you; following means receiving all the messages you write. President Obama has 5.8 million followers and that number goes up all the time. Members of Congress who have Twitter accounts have from a few thousand to a few tens of thousands. For neither the president nor members of Congress do their followers give them broad reach into their constituencies. 5.8 million is a big number, but it is dwarfed by the number of people the president represents. But the followers of the president and of members of Congress have followers. If they retweet the messages they receive to their followers there is an explosion in reach.

One of the attractions of Twitter, which makes it reasonable to assume people will do it, is that it is 140 characters. It is easy to write and easy to read. It is communication that is easy -- very low cost -- for both. And, unlike TV ads, it is cheap.

To show how the two-step could work I counted. I chose a member of the House who had just been re-elected to her second term. She had just under 3,000 followers. That is not very many when compared to the number of her constituents. To count the followers of her followers I excluded everyone from out of state. That produced an interesting result. This member of the House had more followers from outside the US than from her constituency. And she had many more followers from other states than from her constituency. They were all excluded. I also excluded businesses, news media people, and others who seemed unlikely candidates for local organization. That brought the number of followers to 500, which is many fewer than 3,000. Those 500 followers themselves had 150,000 followers. If her followers would forward messages from her, which is very easy to do by clicking on a button, her message would go to another 150,000 people. And that begins to rival the reach of TV. And it gets even bigger than this. This member of Congress tweeted 120 times in the last year. That was 120 times 500 contacts with constituents or 60,000 contacts. There were 338 retweets of her messages. If they went to the average number of their followers that added 101,400 contacts to the 60,000 thousand. If every follower had retweeted each message the total number of contacts would have been 18,060,000 contacts in a single year. And that is a big number.

Retweeting on a big scale does not happen unless you ask. It does not happen unless you give people a sense of how it is important. And it does not happen if you are boring. But the reach can outstrip TV. And it is human communication.

G. R. Boynton is a professor in new media and politics at the University of Iowa.